Carriage for optical elements in an optical sighting device

ABSTRACT

A compact spotting scope includes a housing with an outer surface having a grasping region sized and shaped to fit in the palm of a user&#39;s hand so that the spotting scope can be held at eye level with one hand in an ergonomic arm and wrist position for steady support. An optical element positioned within the housing is adjusted by manually rotating a side-mounted adjustment knob that extends laterally from the outer surface of the housing opposite the grasping region. The side-mounted position of the adjustment knob allows the arm and wrist of the focusing hand to be maintained in an ergonomic position during manipulation of the adjustment knob, thereby further facilitating steady support. An internal support member of the spotting scope includes a frame portion and a generally tubular portion, which are preferably formed together of unitary one-piece construction for aligning optical elements of the spotting scope.

RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.10/425,057, filed Apr. 28, 2003 now U.S. Pat. No. 7,088,506, titledCompact Spotting Scope With Side Focus Control, which is incorporatedherein by reference.

This application is also related to U.S. Design Pat. Application No.29/180,735, filed Apr. 28, 2003, now U.S. Pat. No. D490,097, which isincorporated herein by reference.

BACKGROUND

Spotting scopes are specialized optical telescopes used primarily forterrestrial observation, rather than astronomy, and which include asingle optical path (monocular) and image-inverting optics. As comparedto binoculars, spotting scopes typically have a higher optical power(usually magnifying between 12× and 60×), a narrower field of view, anda larger overall size and weight. While it is often desirable to havethe increased optical power of a spotting scope, the relatively largesize and weight of most known spotting scopes inhibits portability. Thelarge size, relatively large mass, narrow field of view, and highoptical magnification of such spotting scopes generally requires them tobe supported on a tripod or other steady support for effective use.Moreover, most known spotting scopes have a limited operational focusingrange that does not allow a user to focus on targets located closer than30 feet (9.1 meters).

U.S. Pat. No. 4,669,833 of Mise illustrates in FIG. 2 a conventionalfocus adjustment mechanism used in spotting scopes, including a jackscrew that extends through a housing of the scope. The jack screw has anaxis of rotation aligned with an optical axis of the scope and isthreadably engaged with a carriage that supports a prism inside thehousing for linear movement along a pair of guide posts that areprecisely aligned with the optical axis. A knob of the jack screwextends longitudinally from the housing and is manually rotated to drivethe movable prism along the optical axis. A user rotates the jack screwknob by dragging a finger across the top of the knob or by reachingaround the front of the knob to grasp it between the user's thumb andfingers—the latter motion being somewhat awkward. Rotation of the jackscrew drives the carriage at a constant rate throughout the entire rangeof adjustment. The pitch of the jack screw threads is dictated by thefine adjustments required to achieve sharp focus as the focus settingapproaches infinity. However, the present inventors have found that atcloser focusing distances the effect of such fine adjustments are moresubtle, which can make it difficult to quickly visually assess theeffect of adjustments and determine the direction in which the jackscrew should be turned to achieve sharp focus.

The present inventors have recognized a need for an improved spottingscope having a compact size, light weight, and an optical system thatfacilitates hand-held use, thereby eliminating or reducing the need fora tripod or other support device. A need has also been recognized by thepresent inventors for a spotting scope having an optical design thatprovides for improved close focus capabilities and a mechanical designthat facilitates fast adjustment of the focus setting withoutcompromising the user's ability to hold the spotting scope steady.

SUMMARY

A compact spotting scope includes a housing supporting an optical systemthat defines a folded optical path within the housing. The opticalsystem includes a movable optical element, which can be selectivelydisplaced for adjusting an optical setting of the spotting scope, suchas its focus. The spotting scope has a relatively light weight and smallsize to facilitate hand-held use. For example, a preferred embodimentweighs under 16 ounces (˜450 g) and measures less than about 8 inches(˜20 cm) long. Due to its relatively small size and weight, the compactspotting scope can be conveniently carried on a lanyard or other strap.It may also have a wider field of view and less magnification than atraditional spotting scope, to eliminate or reduce the need for a tripodor other steady support device. The housing is configured to fit in thepalm of a user's hand and includes an outer surface having a graspingregion positioned adjacent the folded optical path and sized so that thespotting scope can be held at eye level with one hand in an ergonomicarm and wrist position for steady support.

The spotting scope preferably includes a side-mounted adjustment knoboperably coupled to the optical element for driving the optical elementin response to rotation of the adjustment knob. The adjustment knobextends laterally from the outer surface of the housing opposite thegrasping region and is sized so that the user can comfortably grasp androtate the adjustment knob with his or her free hand. The side-mountedposition of the adjustment knob allows the arm and wrist of the focusinghand to be maintained in an ergonomic position during manipulation ofthe adjustment knob, thereby further facilitating steady support of thespotting scope. The optical element may include an optical focusingelement driven by the side-mounted adjustment knob for a variable rateof movement over the range of focus settings, by employing a mechanismsuch as the orbital drive pin of U.S. Pat. No. 4,643,542 of Gibson orthe spiral cam of U.S. Pat. No. 6,351,907 of Otteman.

In some embodiments, the spotting scope includes optical elements thatcan be adjusted to vary the optical power (magnification) or otheroptical setting of the spotting scope. Power varying optical elementsmay include one or more groups of lenses movable along the optical pathin response to rotation of an eyepiece assembly or objective lens tubeof the spotting scope, for example.

A preferred embodiment implements a novel internal support member foraccurate alignment and compact support of critical optical components ofthe spotting scope. The support member includes a frame portion and agenerally tubular portion, which are preferably integrally formedtogether of unitary molded construction. The tubular portion has alongitudinal axis and at least one guide feature extending along thelongitudinal axis. The guide feature guides a power-varying opticalelement or set of optical elements slidably mounted within the tubularportion, restricting rotation of the power-varying optical element whileallowing movement along the longitudinal axis. In a preferredembodiment, a cam sleeve of the eyepiece assembly is operably coupled tothe power-varying optical element so that rotation of the eyepieceassembly causes the power-varying optical element to move along thelongitudinal axis to adjust the optical power (magnification) of thecompact spotting scope. In alternative embodiments, the optical elementsdriven by the eyepiece assembly adjust a different optical setting ofthe spotting scope, such as a focus setting.

The frame portion of the support member includes a seat that rigidlysupports an optical beam directing element, such as a porro prism, at aprecise position relative to the tubular portion and a precise angularorientation relative to the longitudinal axis of the tubular portion. Asecond optical beam directing element, such as a movable porro prism, ispreferably mounted on a carriage that is slidably supported on a pair ofguide pins press-fit into the support member. The guide pins ensureprecise alignment of the second optical beam directing element relativeto the tubular portion and the first optical beam directing element. Theintegral frame portion and tubular portion of the support member providea shared platform for alignment of the first and second optical beamdirecting elements with other parts of the optical system, such as thepower-varying optical element. These critical optical components can bepre-assembled on the support member in precise alignment and testedbefore installation into the housing, thereby improving the opticalperformance of the compact spotting scope. Advantageously, the frameportion of the support member, the guide pins, and the carriage may becontained entirely within the housing so that the optical beam directingelements are somewhat isolated from the housing to protect the opticalbeam directing elements from shock and external stresses.

Additional aspects and advantages of the invention will be apparent fromthe following detailed description of preferred embodiments, whichproceeds with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a pictorial view of a compact spotting scope in accordancewith a preferred embodiment;

FIG. 2 is a right side elevation view of the compact spotting scope ofFIG. 1;

FIG. 3 is an eyepiece end elevation view of the compact spotting scopeof FIG. 1;

FIG. 4 is a cross section view of the compact spotting scope of FIG. 1taken along lines 4-4 of FIG. 3;

FIG. 5 is an exploded perspective view of the compact spotting scope ofFIG. 1 (reduced scale);

FIG. 6 is an exploded perspective view of a support member and prismassembly of the compact spotting scope of FIGS. 4 and 5;

FIG. 7 is a pictorial view of the assembled support member and prismassembly of FIG. 6 shown from a lower right vantage point;

FIG. 8 is an eyepiece end elevation view of the support member and prismassembly of FIG. 7; and

FIG. 9 is a cross section view of the support member and prism assemblyof FIG. 7 taken along lines 9-9 of FIG. 8; and

FIG. 10 is a pictorial view of the compact spotting scope of FIG. 1 inhand-held use.

In the figures, like reference numerals refer to same or similar partsor features.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Throughout the specification, reference to “one embodiment,” or “anembodiment,” or “some embodiments” means that a particular describedfeature, structure, or characteristic is included in at least oneembodiment. Thus, appearances of the phrases “in one embodiment” or “inan embodiment” or “in some embodiments” in various places throughout thespecification are not necessarily all referring to the same embodimentor embodiments.

Furthermore, the described features, structures, and characteristics maybe combined in any suitable manner in one or more embodiments. Thoseskilled in the art will recognize that certain embodiments may bepracticed without one or more of the specific details, or with othermethods, components, materials and features. In other instances,well-known structures, materials, or operations are shown in simplifiedform or omitted to avoid obscuring aspects of the embodiments.

FIG. 1 is a pictorial view of a compact spotting scope 10 in accordancewith a preferred embodiment. With reference to FIG. 1, spotting scope 10includes a housing 12 within which an optical system is supported. Anobjective lens 16 of the optical system is supported at an objective end18 of housing 12. An eyepiece assembly 20 is mounted at an eyepiece end22 of housing 12 and is preferably rotatable for adjusting an opticalsetting of spotting scope 10, such as magnification. An arrow 24 and/orother indicia may be marked or otherwise displayed at eyepiece end 22 ofhousing to indicate to a user the direction in which to rotate eyepieceassembly 20 to increase or decrease the magnification setting or otheroptical setting of spotting scope 10.

FIGS. 2 and 3 are respective right side elevation and eyepiece endelevation views of spotting scope 10. With reference to FIGS. 1-3, anouter surface 28 of housing 12 includes a grasping region 30 configuredto fit in the palm of a user's hand. Grasping region 30 includes a rightside major surface 34 that spans generally between objective end 18 andeyepiece end 22 of housing. Grasping region 30 further includes aradiused lower corner 38 sized to comfortably nest in the concaveportion of a user's right hand, between the fleshy part of the palm nearthe base of the thumb and the metacarpophalangeal joints, while theuser's fingers extend along right side major surface 34 and over anupper ridge 42 of housing to comfortably grasp spotting scope 10 in onehand for steady support (FIG. 10). Housing 12 and, in particular, rightside major surface 34 and upper ridge 42 are preferably sized and shapedso that one or more of the proximal interphalangeal joints of the user'sright hand (and more preferably the 3rd through 5th proximalinterphalangeal joints) can be smoothly curled about upper ridge 42 ofhousing when lower corner 38 of grasping region 30 is firmly seatedagainst the concave region of the user's palm. For users with very smallhands, the size of housing 12 may require curling of the distalinterphalangeal joints around upper ridge 42.

FIG. 10 is a pictorial view of spotting scope 10 in use. In FIG. 10, adashed line illustrates a folded optical path 44, which is defined bythe optical system of spotting scope 10, as further described below withreference to FIGS. 6-7. Advantageously, containment of folded opticalpath 44 in housing 12 also results in housing 12 being sized and shapedso that outer surface 28 fits comfortably in one hand for stable andwell-balanced support. The size and shape of grasping region 30 (FIGS.2-3) facilitate an ergonomic arm and wrist position to reduce hand andarm fatigue and to inhibit shaking during hand-held use of spottingscope 10. The ergonomic arm and wrist position may include, for example,tucking the elbow against the torso or holding the elbow slightly awayfrom the torso with the forearm in a substantially vertical position toprovide, with the wrist and hand, a pedestal for comfortably supportingspotting scope 10 at eye level. In this position, with the objective endof the folded optical path oriented horizontally, upper ridge 42preferably slopes at an angle θ₁ (FIG. 2) relative to the horizontal andis inclined downwardly away from eyepiece end 22. The slope angle θ1 ofupper ridge 42 is preferably inclined between 2 degrees and 10 degreesand more preferably approximately 5 degrees relative to horizontalsection of folded optical path 44 extending through objective end 18.The slope of upper ridge 42 ergonomically fits the natural positions ofthe interphalangeal joints and provides purchase for comfortably andsecurely grasping spotting scope 10 with fingers curled around upperridge 42. A lower ridge 46 of housing 12 has a corresponding lower slopethat is generally parallel to the slope of upper ridge 42. Lower ridge46 preferably has a slope angle θ₂ inclined between 2 degrees and 10degrees and more preferably approximately 5 degrees relative to thehorizontal section of optical path 44 passing through objective end 18.Lower ridge 46 slopes to generally follow the converging path of lightrays (not shown) entering spotting scope 10 through objective lens 16,thereby reducing the vertical height of right side major surface 34proximal to eyepiece end 22 (between lower corner 38 and upper ridge42), so that grasping region 30 is small enough to fit in the user'shand, as described above.

Skilled persons will understand that grasping region 30 may be made inany of a variety of other shapes that facilitate desirable ergonomichand, arm, and wrist positions. Accordingly, grasping region 30 shouldnot be construed as limited to the particular shape shown in FIGS. 1-3.For example, in one alternative embodiment lower corner 38 (FIGS. 2-3)may have a bulbous shape that is sized to contact a relatively smallarea of the concave portion of the user's palm. In other alternativeembodiments, the grasping region is short enough so that one or more ofthe user's metacarpophalangeal joints rest along upper ridge 42. Instill other alternative embodiments, upper ridge 42 may have a muchlarger or smaller radius around optical path 44 than is depicted in FIG.3. The slopes of upper ridge 42 and lower ridge 46 may also be curved sothat angles θ₁ and θ₂ vary along the length of housing 12.

With reference to FIGS. 1, 2, 3 and 10, a manually adjustable focusingknob 50 projects laterally from a left side 54 of housing 12 oppositegrasping region 30. Focusing knob 50 is manually rotatable about an axisof rotation 56 to drive a movable optical element within housing 12 foradjusting a focus setting of spotting scope 10, as further describedbelow with reference to FIGS. 5-7. Focusing knob 50 and axis of rotation56 extend transversely of an optical axis 100 (FIG. 4) of objective lens16 to define an included angle between axis of rotation 56 and opticalaxis 100 that is preferably 90°. The position of focusing knob 50,projecting from housing 12 transverse (and preferably perpendicular) tothe direction that the spotting scope 10 is aimed when used to view adistant object (not shown), allows focusing knob 50 to be comfortablygrasped and rotated with the user's left hand while maintaining the leftforearm and wrist in an ergonomic position during manipulation offocusing knob 50. The ergonomic hand, wrist, and arm positions reducearm fatigue and shaking of spotting scope 10 when using spotting scope10 to view distant objects. Skilled persons will understand that thearrangement of housing 12 and focusing knob 50 can easily be reversedleft-to-right for an alternative embodiment (not shown), in which thegrasping region comprises a left side major surface for holding in auser's left hand and the focusing knob extends from the right sidesurface of the housing for grasping and rotating with the user's righthand. An alternative optical system (not shown) may also result in adifferent folding arrangement of folded optical path 44.

With reference to FIGS. 2 and 3, a lanyard mount 58 is formed in housing12 and sized to allow a lanyard or strap to be threaded through lanyardmount 58 for carrying spotting scope 10 in the field. Lanyard mount 58is recessed in housing 12 with a bar portion of lanyard mount 58positioned at or below with the outer surface 28 of housing 12 andextending across a well formed in housing 12, which provides clearancefor a lanyard or other strap as it passes around the bar. Housing 12,eyepiece assembly 20, and an objective tube 62 are preferably coated orcovered with an elastomeric armor 90 (FIG. 4) that helps insulate theoptical system from mechanical shock and generally protects spottingscope 10 from damage.

With reference to FIGS. 1 and 2, a threaded mounting hole 66 is providednear objective end 18 of housing 12. Mounting hole 66 provides anattachment point for securing spotting scope 10 to a tripod or othersteady mount. However, spotting scope 10 is preferably of such a lightweight and small size to be particularly suitable to hand-held use. Forexample, spotting scope 10 of the preferred embodiment may weigh lessthan 16 ounces (approximately 450 grams) and measure less than 8 inches(approximately 20 centimeters) in overall length. Spotting scope 10 alsomay feature variable optical power in the range of 10 to 20 timesmagnification, which is sufficiently low enough to make hand-held usepossible with the steady support afforded by the ergonomic graspingregion 30 and side mounted focusing knob 50. Other sizes, weights, andoptical magnification powers may also be suitable for hand-held use. Forexample, another embodiment (not shown), with a larger objective andlonger objective tube, provides variable optical magnification in therange of 15× to 30×, weighs slightly under 22 ounces (approximately 620g), and has an overall length of approximately 10.2 inches(approximately 26 cm).

Mounting hole 66 also provides a convenient place for injecting drynitrogen gas into housing 12 after assembly of spotting scope 10 toprevent condensation or fogging on lenses and other internal opticalsurfaces. After injection of the nitrogen gas, a filling opening (notshown) at the base of mounting hole 66 is sealed with a plug 68 (FIG. 5)to retain a charge of the nitrogen gas within housing 12.

Mounting hole 66 may also be used to attach an auxiliary device (notshown) such as a range finder, illumination device, laserpointer/marker, mounting adapter, bracket, hand strap, or cover, forexample. For example, a tripod mounting adapter 72 (FIG. 5) is securedin mounting hole 66 with a machine screw 74. Tripod mounting adapter 72includes a standard tripod mounting hole on its lower side (not shown)for attachment to a tripod or other steady mount. When mounting hole 66is not in use, a removable cap (not shown) can be inserted or threadedinto mounting hole 66 to prevent dust and debris from becoming lodged inmounting hole 66.

The small size and light weight of spotting scope 10 is achieved, in thepreferred embodiment, using lightweight plastic materials whereverpossible. For example, the preferred arrangement of housing 12 and aninternal support member 120 (FIG. 7) are such that optical elements ofspotting scope can be maintained in accurate alignment without the useof machined surfaces on solid metal supports common to prior-artspotting scopes.

FIG. 4 is a cross section view of compact spotting scope 10 taken alonglines 4-4 of FIG. 3. FIG. 5 is an exploded perspective view of spottingscope 10. With reference to FIGS. 4 and 5, housing 12 includes a mainhousing portion 80 and an eyepiece housing portion 82 that fit togetheralong an interface 84. Main and eyepiece housing portions 80 and 82preferably include structural cores 86 and 88, respectively, over whichan elastomeric armor coating 90 is applied by overmolding or anothersuitable manufacturing process. Structural cores 86 and 88 arepreferably made of an injection molded glass-filled thermoplastic resinfor high strength and reduced weight and cost. Other structuralmaterials may also be used, and need not be molded. A gasket 92 fits ina groove in interface 84 to provide a gas-tight seal between mainhousing portion 80 and eyepiece housing portion 82. Gasket 92 ispreferably made of an elastomeric material such as buna-N, rubber, orsilicone.

A circumferential inner lip 94 is formed in main core 86 at objectiveend 18 for supporting objective lens 16 on housing 12. Objective lens 16is preferably a cemented doublet, but other lens types may beappropriate in a different optical design. An objective O-ring 96 (FIG.5) is interposed between objective lens 16 and main housing portion 80for providing a gas-tight seal. An objective lock ring 98 is threadedonto objective end 18 of main housing portion 80 to secure objectivelens 16 in place. Objective lens 16 includes an optical axis 100 thatextends through the centers of curvature of the optical surfaces ofobjective lens 16 and generally toward a distant object to be viewedusing spotting scope 10. Objective lock ring 98 may include filterthreads 102 for attaching optional optical filters or accessories toobjective end 18. An armored sleeve 104 is fitted around lock ring 98and may be made of an elastomeric material similar to that used forarmor coating 90. To achieve a desired level of durability, lock ring 98is preferably machined of metal and armored sleeve 104 is preferablyattached by stretching and slipping armored sleeve 104 over lock ring98. However, lock ring 98 may also be formed of injection molded plasticor another structural material and armored sleeve 104 may be securedwith adhesive or overmolded directly onto lock ring 98.

A prism assembly 110 is preassembled before installation in main housingportion 80. Prism assembly 110 includes a stationary prism 114 mountedto a frame portion 116 of a support member 120. An optical focusingelement such as a movable prism 124 is supported in a carriage 128,which is slidably mounted on a pair of guide pins 132 and 134. To reduceweight, simplify manufacturing, and reduce cost, support member 120 andcarriage 128 are preferably formed of molded material, such as injectionmolded plastic, molded metal, or die-cast metal. Other inexpensivelightweight structural materials and manufacturing methods may also beused. Guide pins 132 and 134 are supported at one end by support member120. After installation of prism assembly 110 in housing 12, guide pins132 and 134 are supported at their other ends by main housing portion80. A partition 140 of main housing portion 80 extends longitudinallywithin housing 12. Partition 140 shields movable prism 124 and half ofstationary prism 114 from stray light entering through objective 16.Prism assembly 110 is secured to main housing portion 80 by a set ofthree screws 138. Screws 138 extend through holes 142 (FIG. 8) in frameportion 116 and are threaded into threaded metal inserts (not shown)molded into core 86 of main housing portion 80. With reference to FIG.4, frame portion 116 of support member 120 is seated firmly against aledge 144 formed in core 86 of main housing portion 80. Ledge 144accurately locates stationary prism 114 relative to objective lens 16.

Eyepiece housing portion 82 is assembled after screws 138 have beentightened. Eyepiece housing portion 82 fits snugly around frame portion116 of support member 120 and closely mates with main housing portion 80along interface 84 (FIG. 4). A pair of cover screws 146 are insertedthrough mounting holes 148 in ledge 144 and frame portion 116 of (FIG.8), and threaded into a pair of metal threaded inserts (not shown),which are molded inside core 88 of eyepiece housing portion 82. Beforeinstallation of objective lens 16, cover screws 146 are tightened usinga screwdriver or other tool inserted through the open objective end 18of housing 12. Cover screws 146 draw eyepiece housing portion 82 towardmain housing portion 80 to tightly clamp and compress gasket 92therebetween for a gas-tight seal. Objective lens 16 and objective lockring 98 are installed after cover screws 146 have been tightened.

Stationary and movable prisms 114 and 124 are preferably porro prisms.However, other types of optical beam directing elements (also referredto herein as beam steering elements, beam reflecting elements, and beamfolding and reflecting elements), such as roof prisms, other types ofprisms, and/or mirrors may also be used to create folded optical path44. While movable prism 124 is preferably driven to adjust a focussetting of spotting scope, skilled persons will appreciate that prismassembly 110 and a movable optical element of it may be configured orarranged in various other ways not shown, while accomplishing one ormore optical functions. For example, prism assembly 110 may include adifferent type of movable optical element, such as one or morerefractive optical elements. Such a movable optical element may beadjustable for focusing and/or for another optical purpose, such asoptical power adjustment, for example. Additional details andembodiments of prism assembly 110 are discussed below with reference toFIGS. 6-9.

Turning again to FIGS. 4 and 5, an optical power adjustment assembly 150includes movable first and second lens modules 152 and 154 slidablysupported within a rotatable tubular cam sleeve 160. Power adjustinglens assembly 150 preferably utilizes a mechanism for differentialmovement of first and second lens modules 152 and 154, which is similarto the mechanism described in U.S. Pat. No. 3,058,391 of Leupold, issuedOct. 16, 1962, incorporated herein by reference. Lens modules 152 and154 include respective cam followers 162 and 164 (second lens module 154includes two cam followers 164), which are operably engaged withrespective first and second helical cam slots 172 and 174 formed in camsleeve 160. First cam slot 172 preferably comprises a single helicalslot in which a single cam follower 162 rides, whereas second cam slot174 includes an opposing pair of helical slots in which a pair of camfollowers 164 ride. First and second lens modules 152 and 154 arerotatably constrained so that they follow a generally linear path alonglongitudinal axis 194 in response to rotation of cam sleeve 160, tothereby adjust an optical magnification setting of spotting scope 10.Arrow and circle indicia 24 are preferably molded into armor coating 90of eyepiece housing portion 82 to provide a visual indicator of thedirections in which to rotate cam sleeve 160 for increasing anddecreasing the optical magnification setting of spotting scope 10.

Cam sleeve 160 is preferably stepped to include a minor diameter 176 anda major diameter 178 that follow the stepped shape of a tubular portion190 of support member 120. Cam sleeve 160, including minor and majorportions 176 and 178, is preferably machined of a single piece of metalor tubing to provide wear resistance and dimensional accuracy forprecise operation of lens assembly 150. Cam sleeve 160 is preferablymade of metal for durability and wear resistance of first and second camgrooves 172 and 174, but may, alternatively, be formed of anothermaterial such as injection molded plastic. Lens assembly 150 issupported within tubular portion 190 of support member 120 such that camsleeve 160 is rotatable about a longitudinal axis 194 of tubular portion190. After lens assembly 150 is installed in support member 120 andbefore support member 120 is installed in housing 12, a snap ring 198 isattached in a groove 202 at a narrow end 204 of minor diameter portion176 of cam sleeve 160 to retain cam sleeve 160 in tubular portion 190.

First and second lens modules 152 and 154 may include singlets,doublets, or other lens types in various combinations and are preferablyof an optical design that maintains the focus of spotting scope 10constant throughout the range of optical magnification adjustmentafforded by power-adjusting lens assembly 150. The specificprescriptions of the lenses used in lens assembly 150, objective 16, andother lenses and optical elements of spotting scope 10 may be determinedby the dimensions and optical performance requirements of spotting scope10. The lenses and prisms of spotting scope 10 are preferably made ofoptical glass for high resolution imaging, but may, alternatively, bemade of plastic or another material to further reduce the weight andmanufacturing cost of spotting scope 10.

In accordance with the principles described in U.S. Pat. No. 3,058,391,first and second lens modules 152 and 154 are constrained to preventthem from rotating about longitudinal axis 194 so that first and secondlens modules 152 and 154 move along longitudinal axis 194 in response torotation of cam sleeve 160. With reference to FIGS. 4 and 5, first andsecond cam followers 162 and 164 extend outwardly through respectivefirst and second cam grooves 172 and 174 to slidably engage longitudinalguide features 206 (FIGS. 7 and 9) of tubular portion 190, which inhibitrotation of first and second lens modules 152 and 154 about longitudinalaxis 194. First and second helical cam grooves 172 and 174 may have thesame pitch, to thereby drive first and second lens modules 152 and 154at the same linear rate of movement in response to rotation of camsleeve 160. However, in a preferred embodiment, the pitches of first andsecond helical cam grooves of 172 and 174 are different, so that firstand second lens modules 152 and 154 are driven in concert at differentrates of linear movement along longitudinal axis 194, as is typicallynecessary to maintain the focus of spotting scope 10 throughout therange of magnification adjustment.

An ocular lens 210 is seated in a lens holder 212 at a wide end 216 ofmajor diameter portion 178 of cam sleeve 160. An eyepiece tube 220 isthreaded onto cam sleeve 160 via threads 222 and secures ocular lens 210in place at wide end 216 of cam sleeve 160. An ocular O-ring 226 isinterposed between ocular lens 210 and lens holder 212. An eyepieceholder O-ring 228 (FIG. 4) is interposed between lens holder 212 andeyepiece tube 220. The ocular O-ring 226 and eyepiece holder O-ring 228prevent moisture from entering housing 12 around ocular lens 210 andprovide a gas-tight seal for maintaining a dry nitrogen gas chargeinside spotting scope 10 to prevent condensation and fogging on internaloptical surfaces.

An eyepiece lock ring 240 is threadably attached to tubular portion 116of support member 120 via threads 242 and tightened to help clampeyepiece housing portion 82 against main housing portion 80 alonginterface 84. Eyepiece lock ring 240 includes an opening that isslightly larger than the outer diameter of eyepiece tube 220, so thateyepiece lock ring 240 can be installed over eyepiece tube 220. A pairof inner circumferencial grooves 244 are formed in eyepiece lock ring240 and sized to fit a pair of eyepiece tube O-rings 248, which providea dynamic gas-tight seal around eyepiece tube 220 without restrictingrotation of eyepiece tube 220. To reduce friction, lubrication may beapplied between eyepiece tube 220 and eyepiece tube O-rings 248. A lockring O-ring 254 is interposed between eyepiece lock ring 240 andeyepiece housing portion 82 and compressed to provide a gas-tight sealtherebetween. After installation of eyepiece lock ring 240, anelastomeric eyepiece cup 260 is securely fitted around eyepiece tube220. Eyepiece cup 260, which is preferably formed of a resilientelastomeric material, may have sufficient resiliency to provide a tightnon-slip fit around eyepiece tube 220. Adhesive may also be appliedbetween eyepiece tube 220 and eyepiece cup 260 to securely attacheyepiece cup 260. Eyepiece cup 260 includes raised outer ribbing 262 forfacilitating gripping and manual rotation of eyepiece tube 220 foradjusting the magnification setting of spotting scope 10.

Eyepiece tube 220 and eyepiece lock ring 240 are preferably machined ofmetal for dimensional accuracy, strength, durability, and wearresistance. The enhanced strength of metal shields the relatively thintubular portion 190 of support member 120 to protect it from damage. Theuse of metal for eyepiece tube 220 also allows the outer surface ofeyepiece tube 220 to be made very smooth to reduce friction as eyepiecetube 220 slides against eyepiece tube O-rings 248. While lesspreferable, eyepiece tube 220 and eyepiece lock ring 240 may also bemade of plastic or one or more other structural materials.

FIG. 6 is an exploded left-side perspective view of prism assembly 110of spotting scope 10. FIG. 7 is a pictorial view of prism assembly 110shown from a lower right vantage and with movable prism 124 and carriage128 spaced apart from stationary prism 114 and support member 120. FIG.8 is an eyepiece end elevation view of prism assembly 110, and FIG. 9 isa cross-section view of prism assembly 110 taken along line 9-9 of FIG.8. In FIG. 9, movable prism 124 and carriage 128 are shown positionedadjacent support member 120. With reference to FIGS. 6-9, support member120 includes frame portion 116 and tubular portion 190, which arepreferably formed together of unitary one-piece construction. Thecomplex shape of support member 120 is inexpensively manufactured bymolding, for example injection molding of plastic resin, metal injectionmolding, casting, sintering, and other similar methods of manufacture.Molding the support member 120 as an integrated unit results in accuratealignment of tubular portion 190 relative to frame portion 116 forprecisely supporting optical elements in and/or along the folded opticalpath 44. Integration of frame portion 116 and tubular portion 190 alsoreduces the number of parts that must be assembled, which reducesmanufacturing cost and overall weight of spotting scope 10. Tubularportion 190 may have a wall thickness that is considerably thinner thanthe thickness of the walls of frame portion 116. One or more ribs 272around tubular portion 190 connect tubular portion 190 to frame portion116 to provide structural support for the thinner tubular portion 190and the power-adjusting lens assembly 150 it supports. Ribs 272 enhancethe overall structural rigidity of support member 120, which may help tomaintain accurate alignment of prisms 114 and 124 and power-adjustinglens assembly 150 along optical path 44.

Frame portion 116 of support member 120 includes a seat 280 againstwhich stationary prism 114 is securely seated. To ensure precisealignment of stationary prism 114 relative to optical path 44 and toother optical elements of spotting scope 10, support member 120 may beplaced in an assembly fixture (not shown) that is used to establish aprecise lateral position of stationary prism 114 relative to supportmember 120 before applying a drop of epoxy (not shown) betweenstationary prism 114 and frame portion 116 to secure them together. Acompressible pad 282 (FIG. 5) is installed inside eyepiece housingportion 82 and presses against stationary prism 114 to help securestationary prism in place. Pad 282 is preferably made of polyurethanefoam and attached to eyepiece housing portion 82 using apressure-sensitive adhesive. Guide pins 132 and 134 are preferably pressfit into frame portion 116, but other mounting methods may also be used.Movable prism 124 is mounted in carriage 128, which is slidablysupported on guide pins 132 and 134 for movement in response toadjustment of focusing knob 50, as explained below. Movable prism 124 isretained in carriage 128 by an integrally molded resilient spring arm292 of carriage 128. Spring arm 292 presses against movable prism 124 tourge it against a platform portion 296 of carriage 128. Platform portion296 includes a pair of windows 298 through which the optical image pathpasses when entering and exiting movable prism 124.

After movable prism 124 is installed in carriage 128, the lateralposition of movable prism 124 is adjusted relative to carriage 128 toensure precise alignment of stationary and movable prisms 114 and 124.Both stationary and movable prisms 114 and 124 may be adjusted in thismanner in conjunction with a test and alignment fixture (not shown) toensure their precise alignment with each other and relative tolongitudinal axis 194 (FIG. 4) of tubular portion 190. Prealignment ofprisms 114 and 124 ensures precise alignment of optical path 44 withpower-adjusting lens assembly 150 (FIG. 4) when power-adjusting lensassembly 150 is installed in tubular portion 190. After alignment ofmovable prism 124, a drop of epoxy 302 (FIG. 7) or other similarsubstance is applied over spring arm 292 and a top ridge of movableprism 124 to secure movable prism 124 in place on carriage 128.

Guide pins 132 and 134 and main housing portion 80 accommodate a travelpath of movable prism 124 that is sufficiently long enough to providesuperior close focus capabilities. In a preferred embodiment, spottingscope 10 can be focused for viewing objects as close as 10 feet (3meters) and more preferably as close as 6 feet (1.8 meters). Such closefocus capabilities are particularly useful for viewing birds, flowers,and other plants and animals in the field.

With reference to FIG. 6, carriage 128 includes a focusing slot 310 thatextends transversely of guide pins 132 and 134 and longitudinal axis194. Focusing slot 310 is employed in a focus adjustment mechanism 320(FIG. 5), which is similar to the mechanism described in U.S. Pat. No.4,643,542 of Gibson, issued Feb. 17, 1987, incorporated herein byreference. Turning now to FIG. 5, focus adjustment mechanism 320includes a radially offset drive pin 326 that is moved orbitally inresponse to rotation of adjustment knob 50 of focus adjustment mechanism320 about its axis of rotation 56 (FIG. 4). Drive pin 326 extendsthrough a bore 328 of a focusing shaft 332 of focus adjustment mechanism320 and is urged into engagement with focusing slot 310 by a spring 334interposed between drive pin 326 and focusing knob 50. Focusing shaft332 is installed from inside housing 12 through an aperture (not shown)in a turret 336 (FIG. 3) of main housing portion 80. A flange 337 offocusing shaft 332 is larger than the aperture of turret 336 and retainsfocus adjustment mechanism 320 on housing 12. Focusing knob 50 isfastened to focusing shaft 332 by a pair of screws 338. A stop 340formed on the proximal side of focusing knob 50 engages with acorresponding stop groove (not shown) in turret 336 to limit the rangeof rotation of focusing knob 50 and the corresponding range of orbitalmovement of drive pin 326. A cap 342 is applied to focusing knob 50 overscrews 338 to enhance the aesthetic appearance of focusing knob 50 andto prevent tampering with screws 338. Cap 342 may be secured withadhesive or by a mechanical fit with focusing knob 50. Resilient seals346 and 348 are provided for ensuring a gas-tight seal between housing12 and focus adjustment mechanism 320.

In response to orbital movement of drive pin 326, carriage 128 is drivenalong guide pins 132 and 134 to adjust the focus setting of spottingscope 10 in accordance with the principles described in U.S. Pat. No.4,643,542. The orbital path of drive pin 326 results in a relativecarriage velocity that varies depending on the position of adjustmentknob 50 and drive pin 326. For example, carriage 128 moves quickly asdrive pin 326 reaches the top of its orbital path, where drive pin 326,focusing slot 310, and a rotational axis of focus adjustment mechanism320 are in alignment. As drive pin 326 reaches its longitudinal extremes(where focusing slot 310 is tangential to the orbital path of drive pin326), carriage 128 moves more slowly in response to rotation of focusingknob 50. Such a variable velocity profile may advantageously allow auser to find the proper focus setting more quickly than with jack screwmechanisms used in prior art spotting scopes. A variable velocityprofile is particularly useful with the close focus capabilities of thepreferred embodiment. Other focus adjustment mechanisms may also beused. For example, in an alternative embodiment the focus adjustmentmechanism may comprise a spiral cam mechanism of the type described inU.S. Pat. No. 6,351,907 of Otteman, issued Mar. 5, 2002, which isincorporated herein by reference.

While adjustment mechanism 320 is used in the preferred embodiment toadjust a focus setting of spotting scope 10, it may serve other purposesin alternative embodiments (not shown). For example, an alternativeadjustment mechanism may be used for controlling the optical powersetting of spotting scope 10. Skilled persons will appreciate that othermechanical and electromechanical couplings may be implemented foraccomplishing other optical and non-optical adjustments in spottingscope 10. Regardless of the type of adjustment accomplished withadjustment mechanism 320, the side-mounted location of knob 50 andturret 336 facilitate steady hand-held use of spotting scope 10, asdescribed above with reference to FIGS. 3 and 10.

Turning again to FIGS. 6-9, tubular portion 190 of support member 120includes guide features 206 for guiding first and second lens modules152 and 154 of power-adjusting lens assembly 150. In the preferredembodiment shown, guide features 206 include an opposing pair ofelongate guide slots 362 extending longitudinally along the largerdiameter section of tubular portion 190. Guide slots 362 are sized toclosely and slidably receive second cam followers 164 of second lensmodule 154. Guide features 206 also preferably include a single guidechannel 368 molded along the inside surface of the minor diametersection of tubular portion 190. Guide channel 368 is sized to closelyand slidably receive first cam follower 162 of first lens module 152.Guide features 206 are preferably integrally molded into support member120 to reduce the weight and manufacturing cost of spotting scope 10.Skilled persons will understand that guide features 206 need notcomprise slots or channels, but may include, in alternative embodiments(not shown), raised features such as rails or other longitudinallyaligned surfaces against which a cam follower can be guided.

Other optical elements may be used in place of stationary and movableprisms 114 and 124 of prism assembly 110. For example, another type ofbeam directing element, such as a collection of precisely alignedmirrors, may be used to accomplish similar results. Accordingly,stationary and movable prisms 114 and 124 represent only one type of thefixed and movable beam directing elements, respectively, which may beused in the preferred embodiments. Support member 120 and carriage 128might also be useful and advantageous in connection with other beamdirecting elements, such as a roof prism assembly (not shown), or withrefractive optical elements or lenses.

It will be obvious to those having skill in the art that many otherchanges may be made to the details of the above-described embodimentswithout departing from the underlying principles of the invention. Thescope of the present invention should, therefore, be determined only bythe following claims.

1. An assembly for use in an optical sighting device, comprising: amolded support member including a frame portion configured to fitsubstantially within an optical sighting device housing and a generallytubular portion, the tubular portion having a longitudinal axis and atleast one guide feature extending along the longitudinal axis; a firstoptical beam directing element rigidly seated on the frame portion inprecise alignment relative to the tubular portion; a second optical beamdirecting element movably supported on the frame portion in precisealignment relative to the tubular portion and the first beam directingelement; and at least one optical element slidably mounted within thetubular portion of the support member, the optical element including aguide piece operably engaged with the guide feature of the supportmember for guiding movement of the optical element along thelongitudinal axis of the tubular portion.
 2. The assembly of claim 1,further comprising: a guide pin mounted to and extending from thesupport member; and a carriage slidably supported on the guide pin, thesecond optical beam directing element being seated on the carriage. 3.The assembly of claim 2, further comprising a second guide pin mountedto and extending from the support member parallel to the first guidepin, the carriage slidably supported on the first and second guide pins.4. The assembly of claim 1, in which the frame portion and the tubularportion of the support member are integrally formed of unitary one-piececonstruction.
 5. The assembly of claim 4, in which the support member isformed by injection molding.
 6. The assembly of claim 5, in which thesupport member is made of plastic.
 7. A support assembly for preciselysupporting and positioning multiple optical elements inside a housing ofan optical sighting device, comprising: a generally tubular portionhaving a longitudinal axis and at least one guide feature formed thereinfor guiding a first optical element of the optical sighting device formovement along the longitudinal axis; a frame portion configured to fitsubstantially within an optical sighting device housing, the frameportion integrally formed of unitary construction with the tubularsection and including a seat sized to fit at least one optical beamdirecting element for rigidly seating the optical beam directing elementat a precise position relative to the longitudinal axis and in alignmentwith the first optical element; and at least one optical elementslidably mounted within the tubular portion of the support assembly, theoptical element including a guide piece operably engaged with the guidefeature of the support assembly for guiding movement of the opticalelement along the longitudinal axis of the tubular portion.
 8. Thesupport assembly of claim 7, in which the frame portion and the tubularportion are integrally formed of unitary one-piece construction.
 9. Asupport assembly in accordance with claim 8, formed by injectionmolding.
 10. The support assembly of claim 9, in which the frame portionand the tubular portion are made of plastic.
 11. The support assembly ofclaim 7, further comprising a rib connecting the tubular portion to theframe portion for enhancing structural rigidity of the support assembly.12. The support assembly of claim 7, further comprising a carriagemoveably connected to the frame portion, the carriage configured toretain a second optical beam directing element in precise alignmentrelative to the seat and to the longitudinal axis.
 13. An opticalsighting device, comprising: a housing; a molded support memberincluding a frame portion supported within the housing and a generallytubular portion, the tubular portion having a longitudinal axis and atleast one guide feature extending along the longitudinal axis; a firstoptical beam directing element rigidly seated on the frame portion inprecise alignment relative to the tubular portion; a second optical beamdirecting element movably supported on the frame portion in precisealignment relative to the tubular portion and the first beam directingelement; and at least one optical element slidably mounted within thetubular portion of the support member, the optical element including aguide piece operably engaged with the guide feature of the supportmember for guiding movement of the optical element along thelongitudinal axis of the tubular portion.
 14. The optical sightingdevice of claim 13, further comprising a carriage moveably connected tothe frame portion, the carriage configured to retain the second opticalbeam directing element in precise alignment relative to the firstoptical beam directing element and to the longitudinal axis.
 15. Theoptical sighting device of claim 13, further comprising an objectivelens retained within the housing.
 16. The optical sighting device ofclaim 13, wherein movement of the optical element slidably mountedwithin the tubular portion adjusts an optical power of the opticalsighting device.
 17. The optical sighting device of claim 13, whereinthe optical sighting device is a spotting scope.